In the mid-19th century, a fatal natural disaster nearly destroyed the French silk industry, entrusted by French silk merchant Badabio (Alfred Molina). Veteran Harvey (Michael Pitt) left his wife Helene (Keira Knightley) to buy silkworm eggs in Japan. At that time, this was not an easy task, because Japan, which was at the end of the shogunate, was implementing a closed-door policy, so all transactions could only be done in secret. At that time, the powerful aristocratic source Shibingwei (the general department of service) agreed to make the deal in Harvey, but in the negotiation, Harvey was attracted by the concubine (Lu Mingxing). Although the two people do not understand the language, but the fate of love began. With Harvey's four trips, the relationship between the two became deeper and deeper. Helene, who is as far away as France, lives hard as a teacher with her son. Her husband's long journey always worries her. As time went on, Helene gradually realized that Harvey seemed to have a foreign lover.